Question

pts per question) 1. A 2 m piston cylinder device contains nitroen gas at 200 kPa and 350K. Now heat is transferred to the nitrogen in the tank and the pressure of nitrogen rises to 900 kPa and volume is maintained at same. The boundary work done during this process is (a) 1080 kJ (b) 840 k (c)240 k 2. A heat engine receives heat from a source at 727°C and rejiects the waste heat to a sink at 27°C, if heat is rejected from this engine at a rate of 100 kJ/s, the maximum power this heat engine can produce is (d) 0 kJ (a) 233 kW (b) 333 kW (c) 2593 kW (d) 2693 kW 3. A Carnot heat pump supplies heat to a house at a rate of 36000 kh to maintain its temperature constant at 27 C. If the temperature of the outdoors is-3 C, the power required to operate this heat pump is (a) 1 kW (b) 11.1 kW 4. Which factor(s) can cause a process to be irreversible? (c) 3600 kW (d) 59960 kW (a) Mixing of fluids (b) unrestrained compression (c) friction (d) All of them 3. A heat engine cycle is executed with steam in the saturated liquid-vapor mixture region. The pressure of steam is 2 MPa during heat addition and 0.1 MPa during heat rejection. The highest possible efficiency of this heat engine is (a) 47 % (b) 23% (c) 53 % (d) 100% 6. Air at 300 K and 200 kPa is throttled by a valve to a pressure of 100 kPa. If the valve is adiabatic and the change in kinetic energy is negligible, the temperature of air after throttling will be (a) 150 K (b) 200 K (c) 300 K (d) 450 K 7, Steel balls (incompressible substance) at 150°C with a specific heat of 0.50 kJkg Care quenched in an oil bath to an average temperature of 70C at a mass flow rate of 0.3 kgs, and then the rate of heat transfer from the balls to oil is (d) 10.5 kJ/s (c) 48 kJ/s (b) 12 kJ/s (a) 22.5 kJ/s to a volume of 2 L. The boundary R An 8.J. evlinder contains air at 300 kPa and 300 K. Now air is compressed isothermally work done on air during this compression process is (d) 0 k (c) 4.5 kJ (b) 3.3 kJ (a) 1.8 kJ 9, In an insulated tank, 20 kg of hot water at 100 C is mixed with 40 kg of cold water at10C. Both hot water and cold water can be treated as incompressible substance and they their specific heats (c- const) are identical, then the final temperature is (d) 35C (c) 60C (b) 55C (a) 40C 10. Air in a piston-cylinder device is compressed from 2-L and 100 kPa to 500 kPa during a Polytropic process for which Pv3constant. The boundary work done during this compression is (c) 300 J (d) 69 J (b) 248 (a) 2667 J

Answer 1

り2=り」 throtling = 1 d)u McpT /002- heat tranter rom ball to dil T2=T1 ate of mcp AT O.3 X O-5 x ( 150-10) 12 Oork done 3 300 xlo X 3-3271 haat gain by dd ter Heat oss (r00-T)40/T-10) 1OO T -27- 20 T-40 C PVI PLV n-1 RVI n 3. 03, (5 - 300111